a yellow-red solid, Na2S, formed by the reduction of sodium sulphate with carbon (coke) at elevated temperatures. It is a corrosive and readily oxidized material of variable composition and usually contains polysulphides of the type Na2S2, Na2S3, and Na2S4, which cause the variety of colours. It is known in an anhydrous form (...) and as a nonahydrate, ... The compound is deliquescent, soluble in water with extensive hydrolysis, and slightly soluble in alcohol. ...